#region

using System;

#endregion

namespace TvdbLib.SharpZipLib.Zip.Compression.Streams
{
    /// <summary>
    ///     Contains the output from the Inflation process.
    ///     We need to have a window so that we can refer backwards into the output stream
    ///     to repeat stuff.<br />
    ///     Author of the original java version : John Leuner
    /// </summary>
    public class OutputWindow
    {
        #region Fields

        private const int WindowMask = WindowSize - 1;
        private const int WindowSize = 1 << 15;

        private readonly byte[] window = new byte[WindowSize]; //The window is 2^15 bytes
        private int windowEnd;
        private int windowFilled;

        #endregion Fields

        #region Methods

        /// <summary>
        ///     Copy dictionary to window
        /// </summary>
        /// <param name="dictionary"> source dictionary </param>
        /// <param name="offset"> offset of start in source dictionary </param>
        /// <param name="length"> length of dictionary </param>
        /// <exception cref="InvalidOperationException">If window isnt empty</exception>
        public void CopyDict(byte[] dictionary, int offset, int length)
        {
            if (dictionary == null)
            {
                throw new ArgumentNullException("dictionary");
            }

            if (windowFilled > 0)
            {
                throw new InvalidOperationException();
            }

            if (length > WindowSize)
            {
                offset += length - WindowSize;
                length = WindowSize;
            }
            Array.Copy(dictionary, offset, window, 0, length);
            windowEnd = length & WindowMask;
        }

        /// <summary>
        ///     Copy contents of window to output
        /// </summary>
        /// <param name="output"> buffer to copy to </param>
        /// <param name="offset"> offset to start at </param>
        /// <param name="len"> number of bytes to count </param>
        /// <returns> The number of bytes copied </returns>
        /// <exception cref="InvalidOperationException">If a window underflow occurs</exception>
        public int CopyOutput(byte[] output, int offset, int len)
        {
            int copyEnd = windowEnd;
            if (len > windowFilled)
            {
                len = windowFilled;
            }
            else
            {
                copyEnd = (windowEnd - windowFilled + len) & WindowMask;
            }

            int copied = len;
            int tailLen = len - copyEnd;

            if (tailLen > 0)
            {
                Array.Copy(window, WindowSize - tailLen, output, offset, tailLen);
                offset += tailLen;
                len = copyEnd;
            }
            Array.Copy(window, copyEnd - len, output, offset, len);
            windowFilled -= copied;
            if (windowFilled < 0)
            {
                throw new InvalidOperationException();
            }
            return copied;
        }

        /// <summary>
        ///     Copy from input manipulator to internal window
        /// </summary>
        /// <param name="input"> source of data </param>
        /// <param name="length"> length of data to copy </param>
        /// <returns> the number of bytes copied </returns>
        public int CopyStored(StreamManipulator input, int length)
        {
            length = Math.Min(Math.Min(length, WindowSize - windowFilled), input.AvailableBytes);
            int copied;

            int tailLen = WindowSize - windowEnd;
            if (length > tailLen)
            {
                copied = input.CopyBytes(window, windowEnd, tailLen);
                if (copied == tailLen)
                {
                    copied += input.CopyBytes(window, 0, length - tailLen);
                }
            }
            else
            {
                copied = input.CopyBytes(window, windowEnd, length);
            }

            windowEnd = (windowEnd + copied) & WindowMask;
            windowFilled += copied;
            return copied;
        }

        /// <summary>
        ///     Get bytes available for output in window
        /// </summary>
        /// <returns> Number of bytes filled </returns>
        public int GetAvailable()
        {
            return windowFilled;
        }

        /// <summary>
        ///     Get remaining unfilled space in window
        /// </summary>
        /// <returns> Number of bytes left in window </returns>
        public int GetFreeSpace()
        {
            return WindowSize - windowFilled;
        }

        /// <summary>
        ///     Append a byte pattern already in the window itself
        /// </summary>
        /// <param name="length"> length of pattern to copy </param>
        /// <param name="distance"> distance from end of window pattern occurs </param>
        /// <exception cref="InvalidOperationException">If the repeated data overflows the window</exception>
        public void Repeat(int length, int distance)
        {
            if ((windowFilled += length) > WindowSize)
            {
                throw new InvalidOperationException("Window full");
            }

            int repStart = (windowEnd - distance) & WindowMask;
            int border = WindowSize - length;
            if ((repStart <= border) && (windowEnd < border))
            {
                if (length <= distance)
                {
                    Array.Copy(window, repStart, window, windowEnd, length);
                    windowEnd += length;
                }
                else
                {
                    // We have to copy manually, since the repeat pattern overlaps.
                    while (length-- > 0)
                    {
                        window[windowEnd++] = window[repStart++];
                    }
                }
            }
            else
            {
                SlowRepeat(repStart, length, distance);
            }
        }

        /// <summary>
        ///     Reset by clearing window so <see cref="GetAvailable">GetAvailable</see> returns 0
        /// </summary>
        public void Reset()
        {
            windowFilled = windowEnd = 0;
        }

        /// <summary>
        ///     Write a byte to this output window
        /// </summary>
        /// <param name="value"> value to write </param>
        /// <exception cref="InvalidOperationException">if window is full</exception>
        public void Write(int value)
        {
            if (windowFilled++ == WindowSize)
            {
                throw new InvalidOperationException("Window full");
            }
            window[windowEnd++] = (byte) value;
            windowEnd &= WindowMask;
        }

        private void SlowRepeat(int repStart, int length, int distance)
        {
            while (length-- > 0)
            {
                window[windowEnd++] = window[repStart++];
                windowEnd &= WindowMask;
                repStart &= WindowMask;
            }
        }

        #endregion Methods
    }
}